Microsoft is busy this week. Not only did it reveal its own Surface tablets, which will run Windows 8, but today it's previewing its next phone operating system -- Windows Phone 8.

At an event in San Francisco, the software giant showed off the next version of the mobile software, which includes a lot of new features. Joe Belfiore, Microsoft's manager of the Windows Phone program, demonstrated eight of them. He said the next version of Windows Phone 8 will share the same underlying technology of the Windows operating system that will run on tablets, laptops, and desktops.

"Yes, you read that right: Windows Phone 8 is based on the same core technologies that power Windows 8. As a result, Windows Phone 8 will unleash a new wave of features for consumers, developers, and businesses," Belfiore wrote in a post on the Windows Phone blog.

Leading the additions to Windows Phone 8: turn-by-turn navigation and a redesign of Microsoft's home screen. The home screen or Start Screen, which has rectangular tiles to represent apps, will now allow users to change the tile sizes if they're using the phone for many things at once.

At the same time, Microsoft's next version of Windows Phone will support many new hardware specifications. Windows Phone 8 devices will have high-resolution 720p screens, dual- and quad-core processors, and NFC (Near Field Communication) chips. NFC will be built into all Windows 8 phones and will include a new wallet function, so that users can pay for purchases just by tapping their phones at locations that support the standard. There will also be a Tap + Send function so users can tap their Windows Phone 8 phones together to send pictures. Android's Beam function, which is integrated into the new Samsung Galaxy S III, works similarly.

Microsoft is also putting its Skype acquisition to good use in the forthcoming software. Skype and other Voice Over IP (VoIP) services will integrate right into the phone dialer and People or contacts apps. Skype's CEO, Tony Bates, hinted that Skype would also be integrated into Windows 8.

And there's another partnership at work in Windows Phone 8 -- the one between Microsoft and Nokia. The two companies worked closely on Nokia's new Lumia handsets, including the Lumia 900; now they are bringing Nokia's mapping technology to the operating system, including offline maps and turn-by-turn navigation.

Apple demonstrated the next version of its iPhone and iPad operating system -- iOS 6 -- two weeks ago. It includes Apple's own home-brewed maps solution, Facebook integration, and a number of other features. Google is expected to preview the next version of Android -- Jelly Bean -- next week at its Google I/O conference.

Microsoft's Windows Phone software has been competitive with the others in terms of design and ease of use, but not on application selection. Windows Phone only has 100,000 apps in its MarketPlace; Apple has over 500,000 in its App Store. However, Microsoft did announce today that Zynga is bringing Words with Friends and Draw Something to the MarketPlace.

Microsoft did not disclose when Windows Phone 8 would be available and start shipping on phones. It did say that those with Windows Phone devices now won't be able to upgrade to the new operating system. The first wave of Windows Phone 8 phones will be made by Nokia, Samsung, and HTC.